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<a name="GSeekable"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle"><a name="GSeekable.top_of_page"></a>GSeekable</span></h2>
<p>GSeekable — Stream seeking interface</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="GSeekable.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a href="../glib-Basic-Types.html#goffset"><span class="returnvalue">goffset</span></a>
</td>
<td class="function_name">
<a class="link" href="GSeekable.html#g-seekable-tell" title="g_seekable_tell ()">g_seekable_tell</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="GSeekable.html#g-seekable-can-seek" title="g_seekable_can_seek ()">g_seekable_can_seek</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="GSeekable.html#g-seekable-seek" title="g_seekable_seek ()">g_seekable_seek</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="GSeekable.html#g-seekable-can-truncate" title="g_seekable_can_truncate ()">g_seekable_can_truncate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="GSeekable.html#g-seekable-truncate" title="g_seekable_truncate ()">g_seekable_truncate</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GSeekable.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="GSeekable.html#GSeekable-struct" title="GSeekable">GSeekable</a></td>
</tr>
<tr>
<td class="datatype_keyword">struct</td>
<td class="function_name"><a class="link" href="GSeekable.html#GSeekableIface" title="struct GSeekableIface">GSeekableIface</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="GSeekable.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="screen">    <a href="/home/mclasen/gnome/share/gtk-doc/html/gobject/GTypeModule.html">GInterface</a>
    <span class="lineart">╰──</span> GSeekable
</pre>
</div>
<div class="refsect1">
<a name="GSeekable.prerequisites"></a><h2>Prerequisites</h2>
<p>
GSeekable requires
 <a href="../gobject-The-Base-Object-Type.html#GObject-struct">GObject</a>.</p>
</div>
<div class="refsect1">
<a name="GSeekable.implementations"></a><h2>Known Implementations</h2>
<p>
GSeekable is implemented by
 <a class="link" href="GBufferedInputStream.html" title="GBufferedInputStream">GBufferedInputStream</a>,  <a class="link" href="GBufferedOutputStream.html" title="GBufferedOutputStream">GBufferedOutputStream</a>,  <a class="link" href="GDataInputStream.html" title="GDataInputStream">GDataInputStream</a>,  <a class="link" href="GDataOutputStream.html" title="GDataOutputStream">GDataOutputStream</a>,  <a class="link" href="GFileIOStream.html" title="GFileIOStream">GFileIOStream</a>,  <a class="link" href="GFileInputStream.html" title="GFileInputStream">GFileInputStream</a>,  <a class="link" href="GFileOutputStream.html" title="GFileOutputStream">GFileOutputStream</a>,  <a class="link" href="GMemoryInputStream.html" title="GMemoryInputStream">GMemoryInputStream</a> and  <a class="link" href="GMemoryOutputStream.html" title="GMemoryOutputStream">GMemoryOutputStream</a>.</p>
</div>
<div class="refsect1">
<a name="GSeekable.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include &lt;gio/gio.h&gt;
</pre>
</div>
<div class="refsect1">
<a name="GSeekable.description"></a><h2>Description</h2>
<p><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> is implemented by streams (implementations of
<a class="link" href="GInputStream.html" title="GInputStream"><span class="type">GInputStream</span></a> or <a class="link" href="GOutputStream.html" title="GOutputStream"><span class="type">GOutputStream</span></a>) that support seeking.</p>
<p>Seekable streams largely fall into two categories: resizable and
fixed-size.</p>
<p><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> on fixed-sized streams is approximately the same as POSIX
<code class="function">lseek()</code> on a block device (for example: attmepting to seek past the
end of the device is an error).  Fixed streams typically cannot be
truncated.</p>
<p><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> on resizable streams is approximately the same as POSIX
<code class="function">lseek()</code> on a normal file.  Seeking past the end and writing data will
usually cause the stream to resize by introducing zero bytes.</p>
</div>
<div class="refsect1">
<a name="GSeekable.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="g-seekable-tell"></a><h3>g_seekable_tell ()</h3>
<pre class="programlisting"><a href="../glib-Basic-Types.html#goffset"><span class="returnvalue">goffset</span></a>
g_seekable_tell (<em class="parameter"><code><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> *seekable</code></em>);</pre>
<p>Tells the current position within the stream.</p>
<div class="refsect3">
<a name="g-seekable-tell.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>seekable</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="g-seekable-tell.returns"></a><h4>Returns</h4>
<p> the offset from the beginning of the buffer.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="g-seekable-can-seek"></a><h3>g_seekable_can_seek ()</h3>
<pre class="programlisting"><a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
g_seekable_can_seek (<em class="parameter"><code><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> *seekable</code></em>);</pre>
<p>Tests if the stream supports the <a class="link" href="GSeekable.html#GSeekableIface" title="struct GSeekableIface"><span class="type">GSeekableIface</span></a>.</p>
<div class="refsect3">
<a name="g-seekable-can-seek.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>seekable</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="g-seekable-can-seek.returns"></a><h4>Returns</h4>
<p> <a href="../glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if <em class="parameter"><code>seekable</code></em>
can be seeked. <a href="../glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> otherwise.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="g-seekable-seek"></a><h3>g_seekable_seek ()</h3>
<pre class="programlisting"><a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
g_seekable_seek (<em class="parameter"><code><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> *seekable</code></em>,
                 <em class="parameter"><code><a href="../glib-Basic-Types.html#goffset"><span class="type">goffset</span></a> offset</code></em>,
                 <em class="parameter"><code><a href="../glib-IO-Channels.html#GSeekType"><span class="type">GSeekType</span></a> type</code></em>,
                 <em class="parameter"><code><a class="link" href="GCancellable.html" title="GCancellable"><span class="type">GCancellable</span></a> *cancellable</code></em>,
                 <em class="parameter"><code><a href="../glib-Error-Reporting.html#GError"><span class="type">GError</span></a> **error</code></em>);</pre>
<p>Seeks in the stream by the given <em class="parameter"><code>offset</code></em>
, modified by <em class="parameter"><code>type</code></em>
.</p>
<p>Attempting to seek past the end of the stream will have different
results depending on if the stream is fixed-sized or resizable.  If
the stream is resizable then seeking past the end and then writing
will result in zeros filling the empty space.  Seeking past the end
of a resizable stream and reading will result in EOF.  Seeking past
the end of a fixed-sized stream will fail.</p>
<p>Any operation that would result in a negative offset will fail.</p>
<p>If <em class="parameter"><code>cancellable</code></em>
 is not <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>, then the operation can be cancelled by
triggering the cancellable object from another thread. If the operation
was cancelled, the error <a class="link" href="gio-GIOError.html#G-IO-ERROR-CANCELLED:CAPS"><code class="literal">G_IO_ERROR_CANCELLED</code></a> will be returned.</p>
<div class="refsect3">
<a name="g-seekable-seek.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>seekable</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>offset</p></td>
<td class="parameter_description"><p>a <a href="../glib-Basic-Types.html#goffset"><span class="type">goffset</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>type</p></td>
<td class="parameter_description"><p>a <a href="../glib-IO-Channels.html#GSeekType"><span class="type">GSeekType</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>cancellable</p></td>
<td class="parameter_description"><p>optional <a class="link" href="GCancellable.html" title="GCancellable"><span class="type">GCancellable</span></a> object, <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to ignore. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="NULL may be passed as the value in, out, in-out; or as a return value."><span class="acronym">nullable</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>error</p></td>
<td class="parameter_description"><p>a <a href="../glib-Error-Reporting.html#GError"><span class="type">GError</span></a> location to store the error occurring, or <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to
ignore.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="g-seekable-seek.returns"></a><h4>Returns</h4>
<p> <a href="../glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if successful. If an error
has occurred, this function will return <a href="../glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> and set <em class="parameter"><code>error</code></em>
appropriately if present.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="g-seekable-can-truncate"></a><h3>g_seekable_can_truncate ()</h3>
<pre class="programlisting"><a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
g_seekable_can_truncate (<em class="parameter"><code><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> *seekable</code></em>);</pre>
<p>Tests if the stream can be truncated.</p>
<div class="refsect3">
<a name="g-seekable-can-truncate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>seekable</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="g-seekable-can-truncate.returns"></a><h4>Returns</h4>
<p> <a href="../glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if the stream can be truncated, <a href="../glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> otherwise.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="g-seekable-truncate"></a><h3>g_seekable_truncate ()</h3>
<pre class="programlisting"><a href="../glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
g_seekable_truncate (<em class="parameter"><code><a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a> *seekable</code></em>,
                     <em class="parameter"><code><a href="../glib-Basic-Types.html#goffset"><span class="type">goffset</span></a> offset</code></em>,
                     <em class="parameter"><code><a class="link" href="GCancellable.html" title="GCancellable"><span class="type">GCancellable</span></a> *cancellable</code></em>,
                     <em class="parameter"><code><a href="../glib-Error-Reporting.html#GError"><span class="type">GError</span></a> **error</code></em>);</pre>
<p>Truncates a stream with a given <span class="type">offset</span>. </p>
<p>If <em class="parameter"><code>cancellable</code></em>
 is not <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>, then the operation can be cancelled by
triggering the cancellable object from another thread. If the operation
was cancelled, the error <a class="link" href="gio-GIOError.html#G-IO-ERROR-CANCELLED:CAPS"><code class="literal">G_IO_ERROR_CANCELLED</code></a> will be returned. If an
operation was partially finished when the operation was cancelled the
partial result will be returned, without an error.</p>
<p>Virtual: truncate_fn</p>
<div class="refsect3">
<a name="g-seekable-truncate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>seekable</p></td>
<td class="parameter_description"><p>a <a class="link" href="GSeekable.html" title="GSeekable"><span class="type">GSeekable</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>offset</p></td>
<td class="parameter_description"><p>a <a href="../glib-Basic-Types.html#goffset"><span class="type">goffset</span></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>cancellable</p></td>
<td class="parameter_description"><p>optional <a class="link" href="GCancellable.html" title="GCancellable"><span class="type">GCancellable</span></a> object, <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to ignore. </p></td>
<td class="parameter_annotations"><span class="annotation">[<acronym title="NULL may be passed as the value in, out, in-out; or as a return value."><span class="acronym">nullable</span></acronym>]</span></td>
</tr>
<tr>
<td class="parameter_name"><p>error</p></td>
<td class="parameter_description"><p>a <a href="../glib-Error-Reporting.html#GError"><span class="type">GError</span></a> location to store the error occurring, or <a href="../glib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to
ignore.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="g-seekable-truncate.returns"></a><h4>Returns</h4>
<p> <a href="../glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if successful. If an error
has occurred, this function will return <a href="../glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> and set <em class="parameter"><code>error</code></em>
appropriately if present. </p>
</div>
</div>
</div>
<div class="refsect1">
<a name="GSeekable.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="GSeekable-struct"></a><h3>GSeekable</h3>
<pre class="programlisting">typedef struct _GSeekable GSeekable;</pre>
<p>Seek object for streaming operations.</p>
</div>
<hr>
<div class="refsect2">
<a name="GSeekableIface"></a><h3>struct GSeekableIface</h3>
<pre class="programlisting">struct GSeekableIface {
  GTypeInterface g_iface;

  /* Virtual Table */

  goffset     (* tell)	         (GSeekable    *seekable);

  gboolean    (* can_seek)       (GSeekable    *seekable);
  gboolean    (* seek)	         (GSeekable    *seekable,
				  goffset       offset,
				  GSeekType     type,
				  GCancellable *cancellable,
				  GError      **error);

  gboolean    (* can_truncate)   (GSeekable    *seekable);
  gboolean    (* truncate_fn)    (GSeekable    *seekable,
				  goffset       offset,
				  GCancellable *cancellable,
				  GError       **error);

  /* TODO: Async seek/truncate */
};
</pre>
<p>Provides an interface for implementing seekable functionality on I/O Streams.</p>
<div class="refsect3">
<a name="GSeekableIface.members"></a><h4>Members</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="300px" class="struct_members_name">
<col class="struct_members_description">
<col width="200px" class="struct_members_annotations">
</colgroup>
<tbody>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSeekableIface.tell"></a>tell</code></em> ()</p></td>
<td class="struct_member_description"><p>Tells the current location within a stream.</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSeekableIface.can-seek"></a>can_seek</code></em> ()</p></td>
<td class="struct_member_description"><p>Checks if seeking is supported by the stream.</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSeekableIface.seek"></a>seek</code></em> ()</p></td>
<td class="struct_member_description"><p>Seeks to a location within a stream.</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSeekableIface.can-truncate"></a>can_truncate</code></em> ()</p></td>
<td class="struct_member_description"><p>Checks if truncation is supported by the stream.</p></td>
<td class="struct_member_annotations"> </td>
</tr>
<tr>
<td class="struct_member_name"><p><em class="structfield"><code><a name="GSeekableIface.truncate-fn"></a>truncate_fn</code></em> ()</p></td>
<td class="struct_member_description"><p>Truncates a stream.</p></td>
<td class="struct_member_annotations"> </td>
</tr>
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<div class="refsect1">
<a name="GSeekable.see-also"></a><h2>See Also</h2>
<p><a class="link" href="GInputStream.html" title="GInputStream"><span class="type">GInputStream</span></a>, <a class="link" href="GOutputStream.html" title="GOutputStream"><span class="type">GOutputStream</span></a></p>
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